Multicast Transformation:Multicast Transformation is used to create multiple outputs from single input. We often has the situation were we need to load the same data to multiple destinations. Multicast Transformation is the transformation that take single input of data and create multiple copies of data for us to use. Multicast Transformation is synchronous transformation that mean it does not block the data before it transmit to outputs.
I have post that demonstrate how to use Multicast Transformation in our SSIS Packages.
Conditional Split Transformation:
Check this post to see how to use Conditional Split Transformation.
In short, The both transformations accept one input and give us multiple outputs but Multicast Transformation gives us same output on each output what it received as input But Conditional Split will split the data to multiple outputs depending upon the expressions we wrote to divide the data into multiple outputs.